United States: Water surpluses will persist in the Northern Plains

19 February 2020

THE BIG PICTURE
The 12-month forecast ending October indicates moderate to extreme water surpluses in the Dakotas, particularly widespread in South Dakota, with some areas reaching exceptional intensity. Surpluses will extend well into Nebraska and are also forecast in pockets of southern Montana, Wyoming, and Minnesota.

ISciences_United_States_Composite_Adjusted_201911-202010_12mo_panel.png

Around the Great Lakes region Michigan can expect widespread, primarily moderate surplus anomalies in the Lower Peninsula reaching severe intensity in the center and southeast of the state. Moderate surpluses are forecast in pockets of eastern Wisconsin.

Moderate surpluses are also expected in the southern Ohio River Basin in southern Illinois, Kentucky, and Tennessee, and in a few southern states including Mississippi and Georgia. Elsewhere, moderate surplus anomalies are forecast for eastern Oklahoma, a path in southwestern Kansas, and Nevada’s northeast corner. Intense surpluses are forecast in Arizona’s southeast corner and a few other isolated pockets in the Southwest.

The Pacific Northwest can expect deficits of varying intensity reaching into Idaho, with intense deficits in the Columbia River region of south-central Washington and in the Salmon River Mountains of Idaho. Primarily mild deficits are forecast for much of California with severe anomalies in the San Francisco Bay Area and around Fresno, and moderate pockets scattered throughout the state and in pockets of Nevada. Colorado can expect severe to exceptional deficits in the center of the state leading southwest.

Primarily moderate deficits will cover much of the southern half of Texas though anomalies will be severe to extreme along the southwestern border.

In the eastern U.S., moderate to severe deficits are forecast for the Delmarva Peninsula east of Chesapeake Bay; severe deficits around Norfolk, Virginia; and exceptional deficits south of Lake Okeechobee in Florida.

Outside the contiguous U.S., surpluses are forecast for much of Hawaii and moderate deficits in western Puerto Rico. In Alaska, surpluses are forecast in the Koyukuk and Kobuk River regions in the north and in a wide path from the base of the Alaska Peninsula into the center of the state. Some deficits are expected from Anchorage leading east, and also east of Fairbanks.

FORECAST BREAKDOWN
The 3-month maps (below) show the evolving conditions in more detail.

From February through April, surpluses will persist in the Northern Plains States and Upper Midwest with extreme to exceptional anomalies from the Dakotas reaching into Nebraska, and moderate to severe surpluses in Minnesota, Iowa, Wisconsin, and covering lesser extent in Michigan. Some pockets of moderate surplus are expected in Kansas, Oklahoma, and Missouri including along the Missouri River and Upper Mississippi. Surpluses of varying intensity are forecast in southern Montana and in Wyoming. In the Rockies and Southwest, isolated pockets of surplus are forecast in eastern Idaho, Nevada, Arizona, and New Mexico and will include some exceptional anomalies in the Southwest. In the South and Southeast, moderate surpluses are expected in eastern Tennessee and pockets of the Carolinas, Mississippi, Alabama, and Georgia. In Upstate New York, moderate surpluses are forecast near the Finger Lakes Region.

ISciences_United_States_Composite_Adjusted_201911-202010_3mo_panel.png

Intense deficits will shrink but persist in central Colorado and in the Salmon River Mountains of Idaho. Deficits will shrink in the Pacific Northwest and moderate in northern California, though mild deficits will emerge in much of the remainder of California. Deficits will also shrink in Texas but moderate to severe anomalies are forecast in a triangle from Dallas to San Antonio to Houston. Deficits in Florida south of Lake Okeechobee will be severe, downgrading from exceptional. Deficits in northern Virginia and Chesapeake Bay will nearly disappear, while some pockets of deficit will persist in New York State’s northern corner, and in Vermont, New Hampshire, and Maine.

From May through July, anomalies east of the Mississippi will nearly disappear, though moderate surpluses are forecast in the northwestern portion of Michigan’s Lower Peninsula and will emerge in Upstate New York’s northern corner, transitioning from deficit. Though surpluses will downgrade and shrink in the Dakotas and Nebraska, anomalies will remain widespread in South Dakota with some exceptional pockets persisting. Surpluses will shrink in Montana and Wyoming, nearly disappear in Idaho and Nevada, and persist in isolated pockets of Colorado, Arizona, and New Mexico. Colorado’s areas of deficit will normalize. Deficits will become merely mild overall in California, the Pacific Northwest, and Idaho. Moderate deficits will emerge in the Hill Country of Texas in the Edwards Plateau but will nearly disappear in the east.

The forecast for the final months – August through October – indicates surpluses in the Dakotas and Nebraska, and some pockets of generally moderate deficit in the West and along the Lower Brazos River in Texas.

(It should be noted that forecast skill declines with longer lead times.)

IMPACTS
Heavy rainfall in mid-February hit Mississippi’s Pearl River, forcing authorities to open the spillway in the Ross R. Barnett Reservoir north of Jackson and flooding downstream regions. Evacuations were ordered as the river rose 8 feet above flood stage and the governor declared a state of emergency.

Extensive flooding was also reported across eastern Kentucky, necessitating 100 rescue operations and triggering a state of emergency declaration. In Tennessee, a landslide along the Tennessee River claimed two homes and, in a separate incident, blocked a major highway near Great Smoky Mountain National Park. The Tennessee Valley Authority reports that the Valley received 550 percent of its normal rainfall during seven days.

Damage was reported across the Southeast including Virginia, West Virginia, Alabama, and the Carolinas. Weather-related crashes left three people dead.

North Dakota has received a federal disaster declaration, opening up aid dollars, after intense rainfall in October caused flooding, disrupted harvests, and resulted in around $9.7 million worth of damage to public infrastructure. In preparation for a forecast of Spring 2020 flooding, the state insurance commissioner is urging property owners to purchase flood insurance in time to meet a 30-day waiting period required before policies become active.

While the number of property owners in Iowa and Nebraska purchasing federal flood insurance increased by 10 percent this year over last, that number remains well below policies in effect 8 years ago, according to FEMA, and a fraction of those designated “high risk.” The spring flood outlook released by the National Weather Service in mid-February indicates that flood risk is above-average in Nebraska and Iowa.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

Subscribe to our monthly Water Watch List

Search blog categories

Search blog tags